In a PVD film forming apparatus for performing a PVD film forming process on a substrate, e.g., a semiconductor wafer (hereinafter, referred to simply as “wafer”), a target of a film forming material is provided in a processing chamber. The PVD film forming apparatus forms a thin film of the film forming material on the wafer by generating plasma in a processing space, sputtering the target by the plasma, and depositing scattered sputter particles of the film forming material on the wafer. The target is exposed to the processing space and fixed above the wafer so that the scattered sputter particles can be more effectively deposited by gravity (see, e.g., Japanese Patent Application Publication No. 2013-36092).
Recently, there is provided a shutter member to switch execution and stop thin film formation in the PVD film forming apparatus. The shutter member, i.e., a screen member having an opening, is disposed between the processing space and the target. While the thin film formation is stopped, the target is shielded from the processing space. When the thin film formation is executed, the target is exposed to the processing space through the opening facing the target.
A shield member is provided around the target in order to prevent the target and the fixing member from being unnecessarily sputtered by an unintended entrance of the plasma. A clearance between the target and the shield member is set to be very small.
In order to reliably attract the plasma, to the target, a negative voltage is applied to the target. Thus, the target serves as a cathode electrode. If the target is not exactly positioned with respect to the shield member, the gap between the target and an edge of the shield member becomes excessively small. Accordingly, the target and the edge of the shield member are short-circuited by a deposit or the like during the thin film formation. As a result, a negative voltage may also be applied to the processing chamber through the shield member.
For that reason, when a target having, e.g., a rectangular shape is fixed, positioning members such as positioning blocks or the like are provided to be in contact with four side surfaces of the target to precisely position the target with respect to the shield member.
However, when the positioning blocks are made to be in contact with the four side surfaces of the target, thermal expansion of the target during the sputtering is restricted. Accordingly, the target is deformed by an increase of an internal stress, which may result in breakage of the target.
A fine gap may be provided between the positioning blocks and the side surfaces of the target so that the thermal expansion of the target during the sputtering is not restricted. In this case, however, an installation position of the target varies depending on a skill of an operator, and a distance between the target and the edge of the shield member may become excessively small.